The objective of this exploratory grant application is to develop a feasible methodology of isolating candidate prostate epithelial stem cells from the adult rat ventral prostate and growing them in vitro. This objective is based on the hypothesis that the prostate epithelium is derived from a single cell- type progenitor (stem cell). The long-term goal of this research is to establish both normal and transformed cell lines of specific lineages that are derived from the stem cells of the rat prostate epithelium. Two specific aims are proposed: Specific aim 1. Identification and isolation of stem cells in the rat prostate epithelium. We propose to further establish unequivocal evidence to demonstrate that basal cells or a subpopulation of basal cells are the precursor cells of prostate epithelial cells that grow in culture. We will evaluate several isolation procedures of stem cells from the epithelium by taking into consideration the different sedimentation rates, apoptotic rates and putative phenotypic markers of the various cellular components of the prostate epithelium. Specific aim 2. Culture of stem cells. In this specific aim, we will explore avenues by which we will be able to culture and maintain stem cells in vitro as well as begin to define conditions of incubation to generate specific lineages that arise from stem cells.